Electrostatic Repulsion in Van de Graaff Bubbles

A fun look at how Van de Graaff generators illustrate electrostatic forces.

A Van de Graaff generator, invented by American physicist Robert J. Van de Graaff, is a kind of electrostatic generator popular in science demonstrations. For an in-depth look at how these machines operate, please visit our Van de Graaff generator tutorial. Lots of objects – from fluorescent light bulbs to smoke to locks of hair attached to student heads – can be used with the generator to illustrate electrostatic principles. Soap bubbles, as shown in the below tutorial, are also fun to play with.

Blow a bunch of bubbles at the generator by hitting the blue Bubbles button. You’ll see a flurry of bubbles rush toward the machine’s sphere, then make an abrupt about-face in the opposite direction. At first, carrying the charge of the person who blew them, the bubbles are attracted to the charged sphere, which carries the opposite charge. But when that first bubble or two hit the sphere, they absorb its charge and are immediately repelled, popping in the process. Encountering the spray from these burst bubbles, the incoming bubbles will be repelled.